LysR Family Regulator LttR Controls Production of Conjugated Linoleic Acid in Lactobacillus plantarum by Directly Activating the Operon.

Conjugated linoleic acids (CLAs) have attracted more attention as functional lipids due to their potential physiological activities, including anticancer, anti-inflammatory, anti-cardiovascular disease, and antidiabetes activities. Microbiological synthesis of CLA has become a compelling method due to its high isomer selectivity and convenient separation and purification processes. In , the generation of CLA from linoleic acids (LAs) requires the combination of CLA oleate hydratase (CLA-HY), CLA short-chain dehydrogenase (CLA-DH), and CLA acetoacetate decarboxylase (CLA-DC), which are separately encoded by -hy, -dh, and -dc. However, the regulatory mechanisms of CLA synthesis remain unknown. In this study, we found that a LysR family transcriptional regulator, LTTR, directly bound to the promoter region of the operon and activated the transcription of -dh and -dc. The binding motif was also predicted by bioinformatics analysis and verified by electrophoretic mobility shift assays (EMSAs) and DNase I footprinting assays. The overexpression strain showed a 5-fold increase in CLA production. Moreover, we uncovered that the transcription of is activated by LA. These results indicate that LttR senses LA and promotes CLA production by activating the transcription of -dh and -dc. This study reveals a new regulatory mechanism in CLA biotransformation and provides a new potential metabolic engineering strategy to increase the yield of CLA. Our work has identified a novel transcriptional regulator, LTTR, that regulates the production of CLA by activating the transcription of -dh and -dc, essential genes participating in CLA synthesis in This study provides insight into the regulatory mechanism of CLA synthesis and broadens our understanding of the synthesis and regulatory mechanisms of the biosynthesis of CLA.